Cmp pad conditioners and associated methods

ABSTRACT

A method of reducing a degree of compression of a CMP pad during conditioning of the CMP pad comprises engaging the CMP pad with at least one superhard cutting element, the cutting element including a cutting face, the cutting face being angled at 90 degrees or less relative to a finished surface of the CMP pad; and moving the CMP pad and the cutting element relative to one another in a direction resulting in removal of material from the CMP pad with the cutting face to thereby condition the CMP pad.

Priority is claimed of copending U.S. Provisional Patent Application No.60/866,202, filed Nov. 16, 2006, which is hereby incorporated herein inits entirety.

FIELD OF THE INVENTION

The present invention relates generally to CMP pad conditioners used toremove material from (e.g., smooth, polish, dress, etc.) CMP pads.Accordingly, the present invention involves the fields of chemistry,physics, and materials science.

BACKGROUND OF THE INVENTION

Abrasive materials are used in wide range of polishing, planing,dressing, or conditioning processes. As one example, the semiconductorindustry currently spends in excess of one billion U.S. Dollars eachyear manufacturing silicon wafers that must exhibit very flat and smoothsurfaces. Known techniques to manufacture smooth and even-surfacedsilicon wafers are plentiful. The most common of these involves theprocess known as Chemical Mechanical Polishing (CMP) which includes theuse of a polishing pad in combination with an abrasive slurry. Dressingof these CMP pads can be done with a variety of tools.

SUMMARY OF THE INVENTION

In accordance with one embodiment, the present invention provides amethod of reducing a degree of compression of a CMP pad duringconditioning of the CMP pad, comprising: engaging the CMP pad with atleast one superhard cutting element, the cutting element including acutting face, the cutting face being angled at 90 degrees or lessrelative to a finished surface of the CMP pad; and moving the CMP padand the cutting element relative to one another in a direction resultingin removal of material from the CMP pad with the cutting face to therebycondition the CMP pad.

In accordance with another aspect, the present invention provides a padconditioner for removing material from a CMP pad while minimizingcompression of the CMP pad, including a base and a plurality of cuttingelements, extending from the base. The cutting elements can each havinga cutting face angled at 90 degrees or less relative to a finishedsurface of the CMP pad. The faces of the cutting elements can beoriented such that relative movement of the pad conditioner and the CMPpad results in removal of material from the CMP pad with the cuttingfaces to thereby condition the CMP pad.

In accordance with another aspect of the invention, a method of reducinga degree of compression of a CMP pad during conditioning of the CMP padis provided, including: engaging the CMP pad with a plurality ofsuperhard cutting elements formed from a polycrystalline diamondcompact, each of the cutting elements including a cutting face, thecutting faces being angled at 90 degrees or less relative to a finishedsurface of the CMP pad; and moving the CMP pad and the cutting elementrelative to one another in a direction resulting in removal of materialfrom the CMP pad with the cutting face to thereby condition the CMP pad.

There has thus been outlined, rather broadly, various features of theinvention so that the detailed description thereof that follows may bebetter understood, and so that the present contribution to the art maybe better appreciated. Other features of the present invention willbecome clearer from the following detailed description of the invention,taken with the accompanying exemplary claims, or may be learned by thepractice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a pad conditioner in accordance with anembodiment of the invention;

FIG. 2 is a top view of a pad conditioner in accordance with anembodiment of the invention;

FIG. 3A is a partial view of a pad being conditioned in accordance witha PRIOR ART method;

FIG. 3B is a partial view of a pad being conditioned in accordance withan embodiment of the invention;

FIG. 3C is a partial view of a pad being conditioned in accordance withanother embodiment of the invention;

FIG. 3D is a partial view of a pad being conditioned in accordance withanother embodiment of the invention;

FIG. 4 is a perspective view of a portion of a pad conditioner havingcutting elements of varying geometry associated therewith;

FIG. 5 is a side, sectional view of a pad conditioner in accordance withan embodiment of the invention;

FIG. 6A is a photographic, top view of a pad conditioner in accordancewith an embodiment of the invention;

FIG. 6B is a sectional view of the pad conditioner of FIG. 6A;

FIG. 7 is a photograph of a portion of a pad conditioner in accordancewith an embodiment of the invention.

It will be understood that the attached figures are merely forillustrative purposes in furthering an understanding of the invention.The figures may not be drawn or shown to scale, thus dimensions,particle sizes, and other aspects may, and generally are, exaggerated tomake illustrations thereof clearer. Therefore, departure can be madefrom the specific dimensions and aspects shown in the figures in orderto produce the pad conditioners of the present invention.

DETAILED DESCRIPTION

Before the present invention is disclosed and described, it is to beunderstood that this invention is not limited to the particularstructures, process steps, or materials disclosed herein, but isextended to equivalents thereof as would be recognized by thoseordinarily skilled in the relevant arts. It should also be understoodthat terminology employed herein is used for the purpose of describingparticular embodiments only and is not intended to be limiting.

It must be noted that, as used in this specification and any appended orfollowing claims, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise. Thus, forexample, reference to “a cutting element” can include one or more ofsuch elements.

DEFINITIONS

In describing and claiming the present invention, the followingterminology will be used in accordance with the definitions set forthbelow.

All mesh sizes that may be referred to herein are U.S. mesh sizes unlessotherwise indicated. Further, mesh sizes are generally understood toindicate an average mesh size of a given collection of particles sinceeach particle within a particular “mesh size” may actually vary over asmall distribution of sizes.

As used herein, the term “substantially” refers to the complete ornearly complete extent or degree of an action, characteristic, property,state, structure, item, or result. As an arbitrary example, when two ormore objects are referred to as being spaced a “substantially” constantdistance from one another, it is understood that the two or more objectsare spaced a completely unchanging distance from one another, or sonearly an unchanging distance from one another that a typical personwould be unable to appreciate the difference. The exact allowable degreeof deviation from absolute completeness may in some cases depend uponthe specific context. However, generally speaking the nearness ofcompletion will be so as to have the same overall result as if absoluteand total completion were obtained.

The use of “substantially” is equally applicable when used in a negativeconnotation to refer to the complete or near complete lack of an action,characteristic, property, state, structure, item, or result. As anarbitrary example, a cavity that is “substantially free of” foreignmatter would either completely lack any foreign matter, or so nearlycompletely lack foreign matter that the effect would be the same as ifit completely lacked foreign matter. In other words, a cavity that is“substantially free of” foreign matter may still actually contain minuteportions of foreign matter so long as there is no measurable effect uponthe cavity as a result thereof.

As used herein, “base” or “substrate” means a portion of a padconditioner that supports abrasive materials, and to which abrasivematerials may be affixed, or may extend from. Substrates useful in thepresent invention may be any shape, thickness, or material, that iscapable of supporting abrasive materials in a manner that is sufficientprovide a pad conditioner useful for its intended purpose. Substratesmay be of a solid material, a powdered material that becomes solid whenprocessed, or a flexible material. Examples of typical substratematerials include without limitation, metals, metal alloys, ceramics,relatively hard polymers or other organic materials, glasses, andmixtures thereof. Further the substrate may include material that aidsin attaching abrasive materials to the substrate, including, withoutlimitation, brazing alloy material, sintering aids and the like. Thesubstrate and the abrasive cutting elements can, in some embodiments, beformed from the same material and can be formed from an integral, singlepiece of material.

As used herein, “abrasive profile” is to be understood to refer to ashape or a space defined by abrasive materials that can be used toremove material from a CMP pad. Examples of abrasive profiles include,without limitation, rectangular shapes, tapering rectangular shapes,truncated wedge shapes, wedge shapes, and the like. In some embodiments,the abrasive profile exhibited by abrasive segments of the presentinvention will apparent when viewed through a plane in which the CMP padwill be oriented during removal of material from the CMP pad.

As used herein, “superhard” may be used to refer to any crystalline, orpolycrystalline material, or mixture of such materials which has aMohr's hardness of about 8 or greater. In some aspects, the Mohr'shardness may be about 9.5 or greater. Such materials include but are notlimited to diamond, polycrystalline diamond (PCD), cubic boron nitride(cBN), polycrystalline cubic boron nitride (PcBN), corundum andsapphire, as well as other superhard materials known to those skilled inthe art. Superhard materials may be incorporated into the presentinvention in a variety of forms including particles, grits, films,layers, pieces, segments, etc. In some cases, the superhard materials ofthe present invention are in the form of polycrystalline superhardmaterials, such as PCD and PcBN materials.

As used herein, “organic material” refers to a semisolid or solidcomplex amorphous mix of organic compounds. As such, “organic materiallayer” and “organic material matrix” may be used interchangeably, referto a layer or mass of a semisolid or solid complex amorphous mix oforganic compounds. Preferably the organic material will be a polymer orcopolymer formed from the polymerization of one or more monomers.

As used herein, “particle” and “grit” may be used interchangeably.

As used herein, the term “abrasive” can describe a variety of structurescapable of removing (e.g., cutting, polishing, scraping) material from aCMP pad. An abrasive can include a mass having several cutting points,ridges or mesas formed thereon or therein. It is notable that suchcutting points, ridges or mesas may be from a multiplicity ofprotrusions or asperities included in the mass. Furthermore, an abrasivecan include a plurality of individual abrasive particles that may haveonly one cutting point, ridge or mesa formed thereon or therein. Anabrasive can also include composite masses, such as PCD pieces, segmentor blanks, either individually comprising the abrasive layer orcollectively comprising the abrasive layer.

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary.

Concentrations, amounts, particle sizes, volumes, and other numericaldata may be expressed or presented herein in a range format. It is to beunderstood that such a range format is used merely for convenience andbrevity and thus should be interpreted flexibly to include not only thenumerical values explicitly recited as the limits of the range, but alsoto include all the individual numerical values or sub-ranges encompassedwithin that range as if each numerical value and sub-range is explicitlyrecited.

As an illustration, a numerical range of “about 1 micrometer to about 5micrometers” should be interpreted to include not only the explicitlyrecited values of about 1 micrometer to about 5 micrometers, but alsoinclude individual values and sub-ranges within the indicated range.Thus, included in this numerical range are individual values such as 2,3, and 4 and sub-ranges such as from 1-3, from 2-4, and from 3-5, etc.This same principle applies to ranges reciting only one numerical value.Furthermore, such an interpretation should apply regardless of thebreadth of the range or the characteristics being described.

THE INVENTION

The present invention provides systems and methods for use inconditioning CMP pads in manners that greatly improve the quality of theCMP pad conditioning process, as well as decrease the costs and wasterates associated therewith. Generally speaking, the systems and methodsof the present invention provide superior cutting interfaces between thepad conditioners and the CMP pads to thereby reduce the amount ofpressure or force required to maintain cutting (e.g., conditioning) ofthe CMP pad. During conventional, prior art CMP pad dressing orconditioning processes, a large degree of downward is applied to the padconditioner while dressing the pad.

This downward force results in compression of the pad material. As thepad material is generally a relatively pliable material (such aspolyurethane), the downward force often results in the pad materialbecoming much more stiff and resistant to cutting than when in anon-compressed state. The compressed pad material is correspondinglymore difficult to cut smoothly and evenly, with often large pieces beingtorn resulting in asperities being formed in the CMP pad. Theseasperities can damage the silicone wafer to be conditioned by the pad.

Conventional diamond pad conditioners usually include “dull” diamondtips that cut the soft CMP pad with a negative angle (conventionallyused to refer to an angle greater than 90 degrees relative to a finishedsurface applied to the pad, as the tips move away from the finishedsurface). As such, the relatively soft pad must be compressed, resultingin significant deformation (elastic and plastic) before it is penetratedby the diamond tips. Due to the resulting dragging and tearing, thecutting path remaining on the pad is jagged with varying width anddepth.

The present invention can apply multiple cutting tips that can penetratethe soft pad with minimal disruption. This aspect of the inventionbecomes even more critical as CMP pads become softer and gentler inorder to avoid damaging (e.g. dishing, erosion, scratching) the delicateIC during polishing. Some new pads (e.g. Room Haas' Eco Vision) have afull order of magnitude in contact area with the IC wafer so the cuttingduring pad dressing must be clean and effective.

This concept is illustrated in FIG. 3, where a conventional cuttingelement 16 b is shown engaging a CMP pad 14. As with most conventional,prior art cutting elements, the cutting element 16 b includes cuttingfaces 18 b that form an angle α₃ relative to a finished surface to beapplied to the pad that is greater than 90 degrees (relative to thefinished surface to be applied to the pad, as the cutting element movesaway from the finished surface—sometimes referred to as a negativecutting angle). As the cutting element 16 b is pressed downward into thepad, the pad material experiences plastic deformation, resulting in amore stiff response to force applied to the pad material. As such,cutting the pad material is more difficult, and the resulting cutproduces a rough and uneven surface on the pad.

The present invention addresses this issue by reducing the downwardforce required between the pad conditioner and the CMP pad. As a result,the CMP pad is left with a conditioned surface that is much more smoothand level than that obtained using conventional methods.

As shown in the attached figures, in one embodiment of the invention, apad conditioner 12 is provided for removing material from a CMP pad (14in FIGS. 3B through 3D) while minimizing compression of the CMP pad. Theconditioner can include a base 14 and a plurality of superhard cuttingelements 16 extending from the base. As best appreciated from FIG. 3B,the cutting elements can each have a cutting face 18 angled at 90degrees or less relative to a finished surface to be applied to the CMPpad (e.g., relative to movement of the cutting face away from thefinished surface—sometimes referred to as a positive cutting angle). Theface 18 of the cutting element 16 can be oriented such that relativemovement of the pad conditioner (in the direction indicated at 22 inFIG. 3B) and the CMP pad results in clean removal of material from theCMP pad with the cutting face to thereby condition the CMP pad.

By angling the cutting face 18 at 90 degrees or less, relative to afinished surface to be applied to the pad 14, the dressing process cancleanly shave a layer of pad material from the pad. The resultantsurface applied to the pad can be safely used in the CMP process withoutdamaging expensive silicon wafers. The present pad conditioners can beused to shave even a very shallow, thin layer of material from the padand leave behind a clean, smooth and even finished surface on the pad.This technique can be used to remove thin layers of glaze that can beformed on the surface of the CMP pad.

Cutting faces 18 are shown in the figures oriented at angle α₁ of about90 degrees relative to the finished surface to be applied to the CMPpad. Cutting face 18 a of FIG. 3D is oriented at angle α₂ that is lessthan 90 degrees relative to the finished surface to be applied to theCMP pad, on the order of about 60 degrees. The cutting faces can beoriented at a variety of angles, and in one embodiment vary from about45 degrees to about 90 degrees relative to the finished surface of theCMP pad. It has been found that reducing the angle creates an evensharper cutting interface between the cutting element and the pad.

As will be appreciated from the cutting element 16 a of FIG. 3D, and thecutting element shown in the microphotograph of FIG. 7, the cuttingelements can include a distal portion (e.g., a portion furthest from abase of the pad conditioner) and a proximal portion (e.g., a portionclosest to the base). A cross section of the distal portion can be widerthan a cross section of the proximal portion. In other words, in someembodiments of the invention, the cutting element can flare outward (inone or more directions) at a lowermost portion (e.g., a portion to beengaged with the pad). In this manner, the angle of the cutting face canbe decreased below 90 degrees.

The angles of the cutting faces can vary from one embodiment to another.In one aspect, the cutting angle is on the order of about 90 degrees. Inanother aspect, the cutting angle can be slightly larger than 90degrees, on the order of 95 degrees, 100 degrees, and ranges inclusiveof each of these values (e.g., 90-92 degrees, 93-97 degrees, etc.), andincrements falling between these values. In other aspects, the cuttingangle can be on the order of less than about 90 degrees, less than about80 degrees, less than about 75 degrees, less than about 70 degrees, lessthan about 65 degrees, less than about 60 degrees, and ranges inclusiveof each of these values (e.g., 60 degrees to 90 degrees), and incrementsfalling between these values.

While the cutting element 16 a shown in FIG. 3D includes a cutting face18 a that continually tapers outward, it is to be understood that thecutting element can extend downwardly (relative to the orientation shownin the figures) for some distance until flaring outward. Also, a curvedor arcuate slope can be provided to the cutting face, as shown byexample in FIG. 7.

In the aspect of the invention illustrated in FIGS. 3B and 3D, thecutting elements include a trailing edge 24, 24 a that is substantiallyparallel to the finished surface of the CMP pad. In other embodiments,however, such as that shown by example in FIG. 3C, the cutting element16 c can include a trailing edge 24 c that provides a relief areabetween the finished surface of the CMP pad and the cutting element. Inthis manner, the sharpness of the cutting edge 26 c of the blade can beincreased without requiring a sloped or tapering cutting face 18 c.

In addition, while cutting elements 16 shown in FIG. 1 are generallytooth-like, individual projections, in some embodiments of theinvention, the cutting elements can include cutting blades. Thisembodiment is shown by example in FIG. 2, in which cutting elements orblades 16 d are arranged across the face of base 14 d. While not sorequired, the cutting blades can have a cutting length “L” at leasttwice as great as a cutting height (“d” in FIG. 5). The cutting bladescan advantageously be used to remove a larger percentage of pad materialper pass. The cutting blades can also include varying cutting anglesalong the length of the cutting blades, and can include individual teethformed thereon, or therewith. Serrations, protrusions, and the like canalso be formed on or in the cutting blades, or attached thereto, toenhance the cutting ability of the teeth or blades.

The cutting elements of the present invention can be associated with thebase 14 in a variety of manners. In one embodiment, the cutting elementsand the base are formed from an integral piece of material, such as apolycrystalline diamond compact, a polycrystalline cubic boron nitridecompact, and the like. In other aspects, the cutting elements can bebonded, welded or otherwise attached to the base.

Also, various reverse casting methods may be utilized to associate thecutting elements with the base. For example, a spacer layer may beapplied to a working surface of a temporary substrate. The cuttingelements can be arranged so that at least a portion of each the cuttingelements is at least partially embedded in the spacer layer. In oneaspect, the cutting elements can be pressed by a variety of mechanismsor means such that tips of the cutting elements come into contact withthe temporary substrate. In this manner, the temporary substrate candefine the final leveling configuration (e.g., contour) of the finishedpad conditioner/cutting tool. As such, the temporary substrate caninclude varying degrees and combinations of contour, levelness, slope,steps, etc., according to the desired contours of the padconditioner/cutting tool.

An adhesive may be optionally applied to the temporary substrate and/orthe spacer layer and/or the cutting elements to facilitate properarrangement and temporary attachment. The adhesive used on any notedsurface may be any adhesive known to one skilled in the art, such as,without limitation, a polyvinyl alcohol (PVA), a polyvinyl butyral(PVB), a polyethylene glycol (PEG), a pariffin, a phenolic resin, a waxemulsion, an acrylic resin, or combinations thereof. In one aspect, thefixative is a sprayed acrylic glue.

The spacer layer may be made from any soft, deformable material with arelatively uniform thickness, and may be selected according toparticular needs of manufacturing, future use, compositionalconsiderations of tool precursors, etc. Examples of useful materialsinclude, but are not limited to, rubbers, plastics, waxes, graphites,clays, tapes, grafoils, metals, powders, and combinations thereof. Inone aspect, the spacer layer may be a rolled sheet comprising a metal orother powder and a binder. For example, the metal may be a stainlesssteel powder and a polyethylene glycol binder. Various binders can beutilized, which are well known to those skilled in the art, such as, butnot limited to, a polyvinyl alcohol (PVA), a polyvinyl butyral (PVB), apolyethylene glycol (PEG), a paraffin, a phenolic resin, a waxemulsions, an acrylic resin, and combinations thereof.

An at least partially uncured resin material can be applied to thespacer layer opposite of the temporary substrate. A mold, e.g. ofstainless steel or otherwise, may be utilized to contain the uncuredresin material during manufacture. Upon curing the resin material, aresin layer is formed, cementing at least a portion of a cuttingelement. Optionally, a permanent tool substrate may be coupled to theresin layer to facilitate its use in dressing a CMP pad or in otheruses. In one aspect, the permanent substrate may be coupled to the resinlayer by means of an appropriate adhesive. The coupling may befacilitated by roughing the contact surfaces between the permanentsubstrate and the resin layer. In another aspect, the permanentsubstrate may be associated with the resin material, and thus becomecoupled to the resin layer as a result of curing.

The mold and the temporary substrate can subsequently be removed fromthe CMP pad dresser once the resin is cured. Additionally, the spacerlayer can be removed from the resin layer. This may be accomplished byany means known in the art including peeling, grinding, sandblasting,scraping, rubbing, abrasion, etc.

Therefore, the protrusion of the cutting elements from the resin isdependent on the amount covered or concealed by the spacer layer.Additionally, the arrangement of the cutting elements can be relativelyfixed by the resin. As such, the cutting elements can be placed in avariety of configurations, thus creating a variety of configurations ofa surface of an assembled tool.

The cutting elements can be formed in a variety of manners. As mentionedabove, one embodiment includes forming the cutting elements from apolycrystalline diamond compact or a polycrystalline cubic boron nitridecompact (individual cutting elements can be formed from the compacts andattached to the base, or the base and the cutting elements can be formedfrom an integral piece of the compact).

In another aspect, the cutting elements can be formed by creating asintered alumina plate having the basic shape of the cutting elementsextending therefrom. A layer of DLC can be coated over this resultingpatterned surface. Also, CVDD can be coated over a patterned surface ofceramic. In addition, a sintered SiC plate (with molten silicon used toinfiltrate the pores) can be used. In another embodiment, sinteredsilicon nitride (Si3N4) can be used.

In addition, other materials can be used as the cutting element, eitheralone or in combination with other materials, and are to be included inthe scope of the disclosure herein. For example, the cutting element cancomprise or consist essentially of ceramics, or other diamond or cBNfilms, including those deposited via chemical vapor deposition (CVD).Non-limiting examples of ceramics that can be used as a cutting elementinclude alumina, aluminum carbide, silica, silicon carbide, siliconnitride, zirconia, zirconium carbide, and mixtures thereof. Cuttingelements can be, in one embodiment, sintered masses, partially sinteredmasses, and/or layers of material attached to the substrate of the toolprecursor according to any method known in the art. The cutting elementcan, in one aspect, include a mixture, homogeneous or otherwise, of aplurality of materials, optionally including abrasive particles. Inanother aspect, the cutting element can include a plurality of layers ofmaterial. As a non-limiting example, the cutting element can include aceramic overcoated with CVD diamond.

As shown in FIG. 5, each of the cutting elements 16 can include one or aplurality of cutting edges 26 aligned in a common plane 21. Thus, eachof the cutting elements can include four cutting edges, which can eachserve to cut or plane material from a workpiece. By including aplurality of cutting elements, each with a plurality of cutting edges, atotal length of cutting edges per cutting element can be advantageouslyincreased. In addition, since each cutting element is of substantiallythe same height, relative to the working surface of the base, all of thecutting edges from all of the cutting elements can be aligned in thesame common plane. By aligning each of the cutting edges in a commonplane, the cutting device is substantially self-aligned to shave higherregions of the workpiece first, then continue cutting until all “high”points on the workpiece have been reduced, leaving a smooth and flatworkpiece surface.

In addition to finding great utility in dressing CMP pads, the cuttingdevices of the present invention can be utilized in a number of otherapplications, including use in planing substantially brittle materials,such as silicon wafers, glass sheets, metals, used silicon wafers to bereclaimed by planarization, LCD glass, LED substrates, SiC wafers,quartz wafers, silicon nitride, zirconia, etc. In conventional siliconwafer processing techniques, a wafer to be polished is generally held bya carrier positioned on a polishing pad attached above a rotatingplaten. As slurry is applied to the pad and pressure is applied to thecarrier, the wafer is polished by relative movements of the platen andthe carrier. Thus, the silicon wafer is essentially ground or polished,by very fine abrasives, to a relatively smooth surface.

While grinding of silicon wafers has been used with some success, theprocess of grinding materials such as silicon wafers often results inpieces of the material being torn or gouged from the body of thematerial, resulting in a less than desirable finish. This is due, atleast in part, to the fact that grinding or abrasive processes utilizevery sharp points of abrasive materials (which are often not levelrelative to one another) to localize pressure to allow the abrasives toremove material from a workpiece.

In contrast to conventional polishing or grinding processes, the presentinvention can utilize one or more sharply angled cutting edges ofcutting elements to cut material from a workpiece to finish or plane asurface of the workpiece. In general, when a cut is made in a material,the region of the cut will either deform plastically or will crack in abrittle manner. If the plastic deformation is slower than the crackpropagation, then the material is known as brittle. The reverse is truefor ductile deformation. However, under a high pressure, the rate ofcrack propagation is suppressed. In this case, a brittle material (e.g.silicon) may exhibit more ductile characteristics, similar to softmetals. When a sharp cutting edge of the present invention is pressedagainst the surface of brittle silicon, the area of the first contact isextremely small (e.g. a few nanometers across). Consequently, thepressure can be very high (e.g. several GPa). Because the cracks aresuppressed, the sharp diamond edge can penetrate silicon plastically. Asa result, the external energy can be transferred to the very smallvolume of silicon continually to sustain the ductile cutting. In otherwords, the sharp cutting edges can shave or plane silicon in a mannernot previously achieved.

When PCD or PcBN compacts are utilized in the present invention, theresulting cutting elements are generally superhard, resulting in littleyielding by the cutting elements when pressed against a wafer. Ashardness is generally a measure of energy concentration, e.g., energyper unit volume, the PCD or PcBN compacts of the present invention arecapable of concentrating energy to a very small volume without breaking.These materials can also be maintained with a very sharp cutting edgedue to their ability to maintain an edge within a few atoms.

As the ductility of the silicon is maintained by applying pressure to avery small volume, the penetrating radius is generally be keptrelatively small. This is shown by example in FIG. 5, where the depth(or height) of the cutting elements 16 is shown generally by the letter“d” and is on the order of about 0.1 mm. In addition, the shape of thecutting edge must be kept relatively sharp; in some cases with a radiuson the order of 2 nm. In order to accommodate these dual traits, thematerial of the cutting edge of the present invention is hard enough towithstand deformation during the cutting or planing process. In thismanner, both sharpness and hardness of the cutter is realized to ensurethe ductility of the workpiece.

Each of the cutting elements 16 can include a substantially planartrailing face 24 that can define a workpiece contact area. A combinedworkpiece contact area of all of the cutting elements can comprise frombetween about 5% of a total area of the base to about 20% of a totalarea of the base. Thus, in one aspect of the invention, if a pad dresserhas a diameter of about 100 mm, and the combined contact areas of thecutting element will be about 10% of that total, then the total contactarea of all cutting elements can be about 7850 mm². An edge-to-arearatio of each cutting element can be about 4/mm, resulting in a totaledge length being about 31400 mm.

The cutting devices of the present invention can be utilized in either awet system or a dry system. In a dry application, the cutting elementscan be used to cut or plane chips from a workpiece without the presenceof a liquid slurry. In a typical application, the cutting device can bemounted to a holder cushion that can be coupled to a rotatable chuck.The workpiece, for example, a silicon wafer or a CMP pad, can be coupledto a vacuum chuck that provides for rotation of the workpiece. Both therotatable chuck and the vacuum chuck can be rotated in either aclockwise or a counterclockwise direction to remove material from theworkpiece. By changing the rotation of one element relative to another,more or less material can be removed in a single rotation of theworkpiece. For example, if the workpiece and cutting elements arerotated in the same direction (but at different speeds), less materialwill be removed than if they are rotated counter to one another.

In this typical application, a slurry can be applied that can aid inplaning the workpiece surface. The slurry can be either a water slurryor a chemical slurry. In the case where a chemical slurry is used, thechemical can be selected to provide cooling or to react with the surfaceof the workpiece to soften the workpiece to provide a more efficientcutting process. It has been found that the wear rate of a silicon wafercan be dramatically increased by softening its surface. For example, achemical slurry that contains an oxidizing agent (e.g. H₂O₂) may be usedto form a relatively highly viscous oxide that will tend to “cling” onthe wafer surface. In this case, the PCD cutting devices of the presentinvention need not necessarily cut the wafer, but rather can scrape theoxide off the surface of the wafer. Consequently, the sharpness of thecutting edge becomes less critical. In addition, the service life of thecutting device can be greatly extended by utilizing a slurry. Forexample, a PCD scraper used with a slurry may last 1000 times longerthan a PCD cutter.

FIG. 4 illustrates a variety of cutting elements 16 g, 16 h, 16 j inaccordance with an embodiment of the invention. In this aspect of theinvention, the cutting elements can be sized and shaped with rectangularcross sections, oval cross sections, circular cross sections,triangular, polygonal, pyramidal cross sections, etc. The various sizedand shaped cutting elements can be formed by varying locations, andwidths, of grooves cut on the surface of the PCD or PcBN compacts. Whilenot shown in the figures, the cutting elements can also be formed belowthe surface of a PCD or a PcBN compact, such that the cutting elementscomprise inset cavities that include, for example, circular or polygonalshapes.

FIGS. 6A and 6B illustrate another embodiment of the invention in whicha plurality of cutting elements 16 e and 16 f are formed in a PCD base.As can be appreciated from FIG. 6A, the present invention can providefor the integral formation from a superhard polycrystalline material ofcutting elements having differing sizes and configurations. For example,in the embodiment shown, the larger cutting elements 16 e can be used ascutting, planing or dressing elements while the smaller cutting elements16 f can be used primarily as “stopping” elements. In other words, thelarger cutting elements can extend further from the base of the PCD tocut further, or deeper, into the pad (not shown in this figure) on whichthe cutting elements are being used.

When the larger cutting elements 16 e extend sufficiently far, or deep,into the workpiece, the smaller cutting elements can “bottom out” on thesurface of the workpiece to limit further traveling of the largerelements 16 e into the workpiece. To facilitate this concept, the largercutting elements can be made sharper than the smaller cutting elements:for example, they can terminate in an apex point (similar to the cuttingelements shown in FIG. 3C), while the smaller cutting elements canterminate in a flat, planar face (similar to the cutting elements shownin FIG. 3B). In this manner, the larger cutting elements can more easilycut the workpiece than can the smaller cutting elements, causing thesmaller elements to serve as depth “stopping” elements. In this manner,the present invention can provide very accurate control of the depththat the cutting elements cut into a workpiece (e.g., a CMP pad that isbeing dressed).

In addition, as the cutting elements of the present invention can beformed from an integral piece of polycrystalline superhard material,there can remain a useful excess portion of polycrystalline superhardmaterial below the cutting elements on the base of the cutting device(or that forms the base of the cutting device). Thus, in one aspect ofthe invention, once the cutting elements have become dull or damagedduring use, the cutting device can be sharpened by removing a thin layerof the superhard material across the entire face of the cutting devicein the same pattern that was originally created on the face of thedevice. Cutting devices of the present invention can thus be relativelyeasily sharpened or repaired, so long as sufficient polycrystallinematerial remains beneath the cutting elements to allow for furthersharpening of the cutting elements.

EXAMPLES

The following examples illustrate embodiments of the invention that arepresently known. Thus, these examples should not be considered aslimitations of the present invention, but are merely in place to teachhow to make the best-known systems and methods of the present inventionbased upon current experimental data. As such, a representative numberof systems and methods are disclosed herein.

Example 1

A PCD compact with sintered polycrystalline diamond coupled withcemented tungsten carbide substrate is used as a blank for EDMmachining. The compact disk has a diameter of 34 mm (e.g. Adico), 52 mm(e.g. Adico), 60 mm (e.g. Diamond Innovations), 74 mm (e.g. ElementSix), or 100 mm (e.g. Tomei Dia). The typical PCD layer is 400-600microns thick. The total thickness (including the WC substrate) can be1.6 mm or 3.2 mm as standard materials.

The PCD surface is fine polished to have an Ra less than about 1 micron.The blank is wire-EDM cut to form zigzag pattern with tip-to-tipdistance of about 400 microns and tip-to-valley depth of about 100microns. The tip angle can be 60, 70, 60, 90 or 100 degrees (relative toa finished surface applied to a pad), which can be varied by thecomputer setting for traversing the PCD blank. The zigzag patternproduces symmetrical profiles on the vertically sliced blades. The blade(e.g., cutting element) thickness can be less than about 1 mm. If thewire used is thin (e.g. 150 microns) the kerf loss can be minimized sothe number of blades per compact disk is maximized.

The blades can then be cleaned in an ultrasonic bath with micron diamondsuspension to remove all dangling debris, as well as the thermallydegraded surface layer with micro cracks and back converted diamond.

The blade (e.g., cutting element) can then be anchored to a groove moldthat allows the leveling of all cutting tips to within 20 microns.Subsequently, the mold is over cast with epoxy resin to consolidate theblades that are set in a radial pattern on a disk of about 100 mm indiameter by 7 mm thick. The blades can be set with cutting edgesvertical to the mold surface or with a controlled tilt.

As a result, the cutting angle can be adjusted to achieve the optimalgrooving result on the polishing pad. The protrusion of the cutting tipsabove the epoxy matrix is also controlled (e.g. 100 microns). Thisprotrusion can be offset to allow gradual increases of cutting tips. Dueto such a controlled spread of cutting amount, the pad can be cleanedand with terraces of asperities that may achieve optimized polishingeffects.

For example, the high asperities can sweep quickly the protrusion pointsof the copper deposition on the wafer. They will be flattened soon sothe next terrace of asperities can begin polish to make the copperthinner. Finally, the asperities can becoming relatively level to allowbuffing of the already thinned copper layer to remove the barrier layer(e.g. TaN). Current CMP processes would require fast polishing, slowpolishing, and buffing with three consecutive stages. The present padconditioners may, as an option, do all in one stage with significantsaving of manufacturing cost and the boost of production throughput.

Once the above tips become dull, as indicated by the decline of removalrate during the polishing of wafers, the used tips can be recoveredsimply by dissolving in solvent or burning away epoxy matrix. The bladecan then be reset with the other zigzag side for making a new padconditioner. This can significantly reduce the cost of manufacture.Conventional pad conditioners are rarely if ever reused due to theinability to sort out the worn tips from sharp tips.

Example 2

A process similar to that described in Example 1 is used, except that aWC blank is used instead of PCD. The WC blank contains a low amount ofcobalt (e.g. 6 wt %). The straight blades are set in a fixture andplaced in a CVD reactor with methane (1%) hydrogen mixture that isthermally decomposed and dissociated to form carbon and atomic hydrogen.The CVDD coated WC will deposit diamond grains with sharp cutting tipsthat can be spaced by controlling the nucleation density, sparse nucleidistribution, larger grains, and higher protrusion and furtherseparation. The diamond grains can range from nano crystalline (i.e. theedge is straight) to grains with larger than 10 microns. The low cobaltamount in WC can help diamond retaining by avoiding the back conversiondue to its catalystic ability.

Example 3

A process similar to that described in Example 2 is used, except thatthe blade is sliced from a silicon infiltrated SiC blank.

Example 4

A process similar to that described in Example 3 is used, except thatthe blade is sliced from a sintered micron grained Si3N4.

Example 5

A process similar to that described in Example 2 is used, except thatthe blank is made from yttrium toughened zirconia. (ZrO2) with Ti canalso be used as the interface coating buffer for diamond filmdeposition.

It is to be understood that the above-described arrangements are onlyillustrative of the application of the principles of the presentinvention. Numerous modifications and alternative arrangements may bedevised by those skilled in the art without departing from the spiritand scope of the present invention and any appended or following claimsare intended to cover such modifications and arrangements. Thus, whilethe present invention has been described above with particularity anddetail in connection with what is presently deemed to be the mostpractical and preferred embodiments of the invention, it will beapparent to those of ordinary skill in the art that numerousmodifications, including, but not limited to, variations in size,materials, shape, form, function and manner of operation, assembly anduse may be made without departing from the principles and concepts setforth herein.

1. A method of reducing a degree of compression of a CMP pad duringconditioning of the CMP pad, comprising: engaging the CMP pad with atleast one superhard cutting element, the cutting element including acutting face, the cutting face being angled at 90 degrees or lessrelative to a finished surface of the CMP pad; and moving the CMP padand the cutting element relative to one another in a direction resultingin removal of material from the CMP pad with the cutting face to therebycondition the CMP pad.
 2. The method of claim 1, wherein the cuttingface is oriented at about 90 degrees relative to the finished surface ofthe CMP pad.
 3. The method of claim 1, wherein the cutting face isoriented at an angle less than 90 degrees relative to the finishedsurface of the CMP pad.
 4. The method of claim 1, wherein the cuttingface is oriented at an angle greater than 45 degrees and less than 90degrees.
 5. The method of claim 1, wherein the cutting element includesa distal portion and a proximal portion, the proximal portion beingcloser to a base from which the cutting element extends than is thedistal portion, and wherein the distal portion includes a wider crosssection than does the proximal portion.
 6. The method of claim 1,wherein the cutting element includes a cross section and extends from abase, and wherein the cross section of the cutting element includes anarrowed portion intermediate ends of the cutting element.
 7. The methodof claim 1, wherein engaging the CMP pad comprises engaging the CMP padwith a plurality of superhard cutting elements.
 8. The method of claim7, wherein the superhard cutting elements are formed from apolycrystalline diamond compact.
 9. The method of claim 7, wherein theplurality of cutting elements are formed from a polycrystalline cubicboron nitride compact.
 10. The method of claim 1, wherein the cuttingelement includes a trailing edge angled to provide a relief area betweenthe finished surface of the CMP pad and the cutting element.
 11. Themethod of claim 1, wherein the cutting element includes a trailing edgethat is substantially parallel to the finished surface of the CMP pad.12. The method claim 1, wherein the cutting element comprises a cuttingblade having a cutting length at least twice as great as a cuttingheight.
 13. A pad conditioner for removing material from a CMP pad whileminimizing compression of the CMP pad, comprising: a base; and aplurality of superhard cutting elements, extending from the base, thecutting elements each having a cutting face angled at 90 degrees or lessrelative to a finished surface of the CMP pad; the faces of the cuttingelements being oriented such that relative movement of the padconditioner and the CMP pad results in removal of material from the CMPpad with the cutting faces to thereby condition the CMP pad.
 14. The padconditioner of claim 13, wherein each of the cutting faces is orientedat about 90 degrees relative to the finished surface of the CMP pad. 15.The pad conditioner of claim 13, wherein each of the cutting faces isoriented at an angle less than 90 degrees relative to the finishedsurface of the CMP pad.
 16. The pad conditioner of claim 13, whereineach of the cutting faces is oriented at an angle greater than 45degrees and less than 90 degrees relative to the finished surface of theCMP pad.
 17. The pad conditioner of claim 13, wherein each of thecutting elements includes a distal portion and a proximal portion, theproximal portion being closer to a base from which the cutting elementsextend than is the distal portion, and wherein a cross section of thedistal portion is wider than a cross section of the proximal portion.18. The pad conditioner of claim 13, wherein each of the cuttingelements includes a cross section and extends from a base, and whereinthe cross section of the cutting element includes a narrowed portionintermediate ends of the cutting element.
 19. The pad conditioner ofclaim 13, wherein the superhard cutting elements are formed from anintegral piece of a polycrystalline diamond compact.
 20. The padconditioner of claim 13, wherein the plurality of cutting elements areformed from a polycrystalline cubic boron nitride compact.
 21. The padconditioner of claim 13, wherein each of the cutting elements includes atrailing edge angled to provide a relief area between the finishedsurface of the CMP pad and the cutting element.
 22. The pad conditionerof claim 13, wherein the cutting element includes a trailing edge thatis substantially parallel to the finished surface of the CMP pad. 23.The pad conditioner of claim 13, wherein the cutting element comprises acutting blade having a cutting length at least twice as great as acutting height.
 24. A method of reducing a degree of compression of aCMP pad during conditioning of the CMP pad, comprising: engaging the CMPpad with a plurality of superhard cutting elements formed from apolycrystalline diamond compact, each of the cutting elements includinga cutting face, the cutting faces being angled at 90 degrees or lessrelative to a finished surface of the CMP pad; and moving the CMP padand the cutting element relative to one another in a direction resultingin removal of material from the CMP pad with the cutting face to therebycondition the CMP pad.
 25. The method of claim 24, wherein the cuttingelements extend from a base, and wherein the base and the cuttingelements are formed from an integral piece of a polycrystalline diamondcompact.